JP2562061B2 - Low loss oxide magnetic material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECT OF THE INVENTION [Industrial field of application] The present invention relates to a low loss oxide magnetic material which is a core material mainly for transformers, which is used at a high frequency for a switching power supply for electronic devices and the like, and particularly 30 to 40 mol% as a main component. Manganese monoxide (MnO), 5-15 mol% zinc oxide (Zn
O), and ferric oxide (Fe ₂ O ₃ ) as the balance, and 0.02 to 0.15% by weight of calcium oxide (CaO) as a secondary component,
And a low loss oxide magnetic material containing 0.005 to 0.100% by weight of silicon oxide (SiO ₂ ).

[Conventional technology]

Manganese-zinc-based ferrite, which is an oxide magnetic material, is widely used as a core material for transformers and coils of various communication devices, consumer devices, etc. A low loss oxide magnetic material with a main component of 30 to 100 kHz is used.
40 mol% of MnO, 5 to 15 mol% of ZnO, residue comprises Fe ₂ O _3, 0.02 to 0.15 wt% of CaO as an auxiliary component, 0.005 to 0.
Those containing 100% by weight of SiO ₂ have already been developed.

[Problems to be Solved by the Invention]

However, in recent years, in order to reduce the size and weight of switching power supplies, there is an increasing tendency to use switching frequencies at high frequencies of 100 kHz or higher, and low-loss oxide magnetic materials as core materials for transformers with performance that meets the purpose are being used. Is required.

On the other hand, when a low-loss oxide magnetic material having the above-mentioned conventional components is used as the core material of a transformer for a switching power supply with a switching frequency of 100 kHz or more, the power loss (P _B [kW / m ³ ]) is large and the temperature rises above the permissible temperature due to the heat generated by this, and there is a drawback that the transformer itself and surrounding parts are damaged and cannot be used.

Therefore, the object of the present invention is to use a low-loss oxide magnetic material that can be put to practical use by suppressing the heat generation to a temperature below the allowable temperature even if the frequency is used at a high frequency of 100 kHz or more and the iron loss is small and therefore the power loss is small. To provide.

B. Structure of the Invention [Means for Solving the Problems] The present invention provides a conventional low-loss oxide magnetic material containing a main component and a sub-component already developed by adding an oxide of another component, It is intended to obtain a low-loss oxide magnetic material in which iron loss of 100 kHz or more is further reduced than before.

That is, the present invention is, as the main component of the oxide magnetic material obtained by mixing, molding and firing oxide powder, 30-40 mol% manganese monoxide (MnO), 5-15 mol% zinc oxide (ZnO) ,
And ferric oxide (Fe ₂ O ₃ ) as a residue, and 0.02 to 0.15% by weight of calcium oxide (CaO) as a secondary component, and
In a low-loss oxide magnetic material containing 0.005-0.100 wt% silicon oxide (SiO ₂ ), further 0.05-0.30 wt% (not including 0.05%) zirconium dioxide (ZrO ₂ ), 0.
Low, characterized by the addition of less than 50% by weight (not including 0%) aluminum trioxide (Al ₂ O ₃ ) and less than 0.30% by weight (not including 0%) titanium dioxide (TiO ₂ ). It is a lossy oxide magnetic material.

[Action]

The present invention provides conventional low-loss oxide magnetic materials with zirconium dioxide (ZrO ₂ ), aluminum trioxide (Al ₂ O ₃ ),
As a result of conducting a series of experiments in which titanium dioxide (TiO ₂ ) and titanium dioxide (TiO ₂ ) were added in various proportions, it was found that in the materials added in the above component range, low loss oxidation that reduced iron loss of 100 kHz or more and reduced power loss. A magnetic material is obtained.

The additive ZrO ₂ is extruded at the grain boundary of the low loss oxide magnetic material structure to increase the specific resistance of the grain boundary, and the additive Al ₂ O ₃ and T
It is considered that iO ₂ has a function of forming a solid solution in the crystal and increasing the specific resistance inside the crystal, and that the additive Al ₂ O ₃ has a function of making the crystal structure uniform.

Due to these combined effects, the low-loss oxide magnetic material containing them is made uniform in the electromagnetic characteristics inside the tissue and the specific resistance ρ of the entire tissue is further increased, which causes eddy current loss related to iron loss. Is considered to have decreased and the power loss has decreased. Due to the reduction of power loss, heat generation at high frequencies is suppressed.

Actually, a detailed experiment was performed on the low loss oxide magnetic material in the vicinity of the addition component range of the present invention, and when the sample was evaluated, as compared with the conventional low loss oxide magnetic material of the above component, for example, ZrO ₂ 0.10 wt. %, Al ₂ O ₃ 0.05% by weight, and TiO ₂ 0.05% by weight, it was confirmed that the low-loss oxide magnetic material has a specific resistance ρ of 10 times or more and a power loss of 200 kHz or less.

〔Example〕

The contents of the experiment for the examples and comparative examples of the present invention will be described in detail below.

As the main component of the oxide magnetic material formed by mixing, molding and firing oxide powder, 53.0 mol% ferric oxide (Fe
₂ O ₃ ), 36.0 mol% manganese monoxide (MnO), and 11.0
Contains standard components of mol% zinc oxide (ZnO), with secondary components silicon dioxide (SiO ₂ ) and calcium oxide (CaO)
In the composition range of the conventional low-loss oxide magnetic material, and a plurality of present examples in which zirconium dioxide (ZrO ₂ ), aluminum trioxide (Al ₂ O ₃ ), and titanium dioxide (TiO ₂ ) were added in combination. Various samples of the low-loss oxide magnetic material were manufactured. Further, samples of low-loss oxide magnetic materials of the conventional comparative example in which the latter three oxides were not added and a plurality of other comparative examples in which the latter three oxides were added alone or in combination were manufactured. Each oxide raw material was added and mixed with a predetermined amount of components, granulated, molded and pressed, then oxygen partial pressure of 5.0 at% or less in a nitrogen gas atmosphere, and sintered at a temperature of 1300 to 1400 ° C. in this example and A sample of the comparative example was obtained.

Table 1 shows the contents of sub-components and additive components and the
It shows the minimum value of the power loss P _B with respect to the sample temperature when the maximum magnetic flux density Bm is 1000 G at 200 kHz.

According to Table 1, zirconium dioxide (ZrO ₂ ), aluminum trioxide (Al ₂ O ₃ ), and titanium dioxide (TiO ₂ ).
It can be seen that the power addition loss is reduced compared to the conventional comparative sample No. 1 by the combined addition of. This is because these additives cause ZrO ₂ to break out into the grain boundaries of the structure inside the structure of the low-loss oxide magnetic material, increasing the resistivity of the grain boundaries, and Al ₂ O 3
_{It is considered that 3} and TiO ₂ had a solid solution in the crystal to increase their specific resistance, and Al ₂ O ₃ had the effect of making the crystal structure uniform. It is considered that the homogenization and the specific resistance of the entire structure were increased, which reduced the iron loss and the power loss.

Sample No. 11 containing 0.40 wt% zirconium dioxide (ZrO ₂ ), Sample No. 15 containing 0.60 wt% aluminum trioxide (Al ₂ O ₃ ) and 0.040 wt% titanium dioxide (TiO ₂ ). For sample No. 19, abnormal grain growth was observed, and it is considered that the power loss was increased,
It is understood that the content of each additive component is preferably less than this value.

Also, it is understood that the comparative sample Nos. 2 to 7 in which at least one of these added components is 0% has a relatively large power loss and a small effect.

Table 2 shows the initial magnetic permeability μ, the saturation magnetic flux density B ₁₅ , the residual magnetic flux density Br, and the low loss oxide magnetic materials of the sample No. 8 of this example and the sample No. 1 of the conventional comparative example. And specific resistance ρ
3 shows a comparison of the respective electromagnetic characteristics.

When comparing the electromagnetic characteristics of the sample No. 8 of the example in Table 2 and the sample No. 1 of the comparative example, the specific resistance of the sample No. 8 is about 10 times or more. As a result, it is understood that the iron loss due to the eddy current loss is reduced and the power loss is reduced. Further, the magnetic properties are almost the same, which shows that they are excellent as the core material for this type of transformer.

From the above, according to the embodiment of the present invention, the power loss at 200 kHz is significantly reduced, and a very excellent low loss oxide magnetic material is used as the core material of the switching power supply transformer at 100 kHz or more. It was confirmed that it was obtained.

C. EFFECTS OF THE INVENTION [Effects of the Invention] As described above, according to the present invention, various characteristics required as a core material for a transformer for a switching power supply are sufficiently satisfied, and power loss is significantly increased at a frequency of 100 kHz or more. A low loss oxide magnetic material that can be reduced can be provided.

Claims (1)

(57) [Claims] 1. A main component containing 30 to 40 mol% of manganese monoxide (MnO), 5 to 15 mol% of zinc oxide (ZnO), and the balance of ferric oxide (Fe ₂ O ₃ ). , 0.0 as an accessory ingredient
2 to 0.15 wt% calcium oxide (CaO), and 0.005 to
In a low loss oxide magnetic material containing 0.100% by weight of silicon oxide (SiO ₂ ), further 0.05 to less than 0.30% by weight (0.05
% Of zirconium dioxide (ZrO ₂ ), less than 0.50% by weight (not including 0%) of aluminum trioxide (Al)
₂ O ₃ ) and less than 0.30% by weight (not including 0%) of titanium dioxide (TiO ₂ ), a low loss oxide magnetic material.